Piston primer cartridge with improved one piece primer

ABSTRACT

An improved cartridge having a movable single-unit piston primer and an associated firing pin arrangement is disclosed for use in automatic and semi-automatic firearms which operate on the principle of primer set-back. The movable single-unit piston primer is cup-shaped and open toward the propellant-containing interior of the cartridge casing and contains a primer mixture but is devoid of a conventional anvil. The movable piston primer has a unitary integral cup having a tubular side wall and a relatively thinner and more deformable integral web-like closed base wall at the rearward end and with an annular flared flange portion formed at the forward open end which is adapted to obturate upon ignition of the propellant to provide a sliding gas seal and limit the rearward longitudinal movement of the primer by engaging an annular shoulder formed in the cartridge casing.

[111 3,7,426 ,ioly 11,i973

[ PISTON PRIIMER CARTRIDGE WITH IMPROVEE ONE PIECE PRIMER [75] Inventor: llrwin R. Earr, Lutherville, Md. [73] Assignee: AAll Corporation, Cockeysville, Md.

[22] Filed: Oct. 29, 11971 [21] Appl. No.: 193,921

Related US. Application Data [63] Continuation of Ser. No. 849,649, Aug. 13, 1969,

abandoned.

[52] US. Ci. 1112/38, 102/45 [51] int. Cl F42b 5/02 [58] Field oi Search 102/38, 45, 44, 49.7, 102/43, 43 F [56] Reterences (Iited UNITED STATES PATENTS 624,146 5/1899 Young 102/38 831,132 9/1906 Young et a1. 102/45 2,407,264 9/1946 Ferrel l02/49.7 3,477,375 11/1969 Barr 102/45 3,486,453 12/1969 Smallwood 102/45 3,477,374 11/1969 Barr 102/45 FOREIGN PATENTS OR APPLICATIONS 179,581 5/1922 Great Britain I 5 l 3 b 309,1 l4 5/1929 Great Britain Primary Examiner-Robert F. Stahl Att0meyReginald F. Pippin, Jr.

[57] ABSTRACT An improved cartridge having a movable single-unit piston primer and an associated firing pin arrangement is disclosed for use in automatic and semi-automatic firearms which operate on the principle of primer setback. The movable single-unit piston primer is eupshaped and open toward the propellant-containing interior of the cartridge casing and contains a primer mixture but is devoid of a conventional anvil. The movable piston primer has a unitary integral cup having a tubular side wall and a relatively thinner and more deformable integral web-like closed base wall at the rearward end and with an annular flared flange portion formed at the forward open end which is adapted to obturate upon ignition of the propellant to provide a sliding gas seal and limit the rearward longitudinal movement of the primer by engaging an annular shoulder formed in the cartridge casing PAIENIEU JUL 1019B 3' 744 420 Irwin R. Barr INVENTOR ATTORNEY PISTON PRIMER CARTRIDGE WITH IMPROVED ONE PIECE PRIMER This application is a continuation of my co-pending application Ser. No. 849,649 now abandoned, filed Aug. 13, 1969.

This invention relates to gun or other weapon-fired and usable cartridges having percussive primers, and particularly to a cartridge employing an anvil-less primer with a unitary integral cup, taking its form in an illustrative embodiment as a cartridge with a piston primer of this character.

In automatic or semi'automatic firearms utilizing primer set-back cartridges for operation, a cartridge may be chambered in the barrel, and when the firing pin of the firearm strikes the primer in a. forward stroke, a primer charge ignites which, in turn, fires a propellant to creat a high gas pressure that propels a projectile forward from the cartridge casing and through the barrel. The high gas pressure also propels the primer rearwardly in a direction opposite to the motion of the projectile. The rearward movement of the primer imparts energy to the firing pin and drives it rearwardly in a return stroke that operates the breech mechanizm to extract the spent cartridge casing, cock the firearm, and chamber another cartridge.

While movable piston primer cartridge arrangements have long existed, all such primers have had an anvil of some type, in the sense of being one of two discrete and relatively movable interfacing parts or elements forming and/or lying within the effective primer mixture containment and percussive firing movement zone, one of which discrete parts or elements acts in the nature of an anvil for percussive striking by, and/or percussive sliding surface interaction with, the other discrete element, and such has also been the case with cartridges employing fixed primers and which primers retain their structural integrity whether the anvil be a circumferential rim-like anvil, a unitary conventional conical anvil, an internal corrugated sheet at and facing a portion of the rear wall of the primer cup for relative motion therebetween, or some other type to enable the firing pin to ignite the primer charge, which in turn fires the propellant to create the high gas pressure. To obtain the simplest and least expensive gun-cartridge usable movable primer set-back cartridge, it is desirable that the primer be easily and simply constructed of as few parts as possible to facilitate the manufacture of the cartridge and hence reduce production costs. Primers of this nature differ fundamentally from stab detonators commonly used in explosives detonation or other work, in that the stab detonators are fired by stab penetration of the detonator containment body and direct penetration of the firing mix by a sharp pointed stab pin to cause firing of the firing mix therein, with resultant destruction of the stab detonator containment body integrity and escape of the gases therethrough, independent of its subsequent total destruction by the further compound which may be detonated or fired thereby.

In addition, to obtain the most effective operation of a primer set-back arrangement it is necessary to use a cartridge which maximizes the amount of energy the primer imparts to the firing pin of the firearm during the return stroke. This can best be done by minimizing the loss of energy resulting from the friction between the primer and the cartridge casing which is inherent in a cartridge of the type utilizing a movable primer to drive a firing pin backward in a return stroke, while at the same time preventing the propellant gas from leaking rearward of the primer which results in a substantial reduction in the differential gas pressure exerted on the primer and which is particularly a problem in cartridges utilizing a movable primer because of the necessity to use some type of movable gas seal which inherently introduces an element of friction in the rearward movement of the primer. Furthermore, it is desirable, and in fact necessary from a normal practical weapon cartridge use standpoint, to fire the primer without rupturing its containment body and to prevent the primer from rupturing or destroying its structural gascontainment integrity or being blown out the base of the cartridge upon firing, because the resulting sharp reduction of the propellant gas pressure would substantially reduce the velocity of the projectile and hence affect the range and accuracy of the weapon.

Accordingly, it is a feature of the present invention to provide a cartridge of the primer set-back type having a movable primer with a simple, compact and integral construction to facilitate the manufacture of the cartridge and reduce the production costs.

It is another feature of the present invention to pro vide a cartridge of the primer set-back type wherein energy losses due to the friction between the movable primer and the cartridge casing are avoided while efficiently translating propellant gas pressure action into a rearward driving force on the primer, thereby enabling a maximum driving force to thereby enabling be imparted to the firing pin of the firearm during a return stroke.

It is a further feature of the present invention to provide a movable primer which engages the cartridge casing in a manner that prevents the rearward leakage of the high pressure propellant gas to further maximize the amount of force exerted on the piston primer and also prevent the primer from being blown out the base of the cartridge by the propellant gas force, to avoid a sharp reduction in the propellant gas pressure.

Still another feature of the present invention is to provide a weapon-usable cartridge having a percussive primer as a part thereof, which primer has an integral one-piece cup formed of malleable material which does not disintegrate or rupture on firing, and which primer cup has a compact primer mixture mass therein, as distinguished from a detonator or detonating mixture or chemical, as such terms are normally used in the ordnance art, and which integral-one-piece-cup primer is devoid of an anvil in any normal sense of the word, whereby to substantially reduce the number of primer parts and cost of production, while retaining the essential operational features of structural integrity, percussive firing pin firing within the range of normally acceptable firing pin energies, and the enablement of use of relatively and acceptably safe primer mixtures.

In the illustrative cartridge the integral one-piece cup anvil-less primer has a construction enabling it to function as a movable piston. Thus, in the presently illustrated embodiment a cartridge is provided having a casing with a pair of longitudinally arranged coaxial bores connected by an annular beveled shoulder with the larger diameter bore being formed in the forward portion of the casing and containing a propellant and with the smaller diameter bore being formed in the base portion of the casing and having a movable cup-shaped piston primer disposed therein which opens toward the interior of the casing and contains a primer mixture adapted to be ignited to fire the propellant in the larger diameter bore. The movable cup-shaped piston primer has a deformation-resistant tubular wall portion freely slidably engaging the smaller diameter bore with a relatively thinner and more easily deformable web-like base portion at the rearward end thereof which is adapted to be indented upon being struck by the head of the firing pin to ignite the primer charge. At the open end of the tubular wall portion is formed an annular flared obturating flange portion with only a small circumferential surface area slidably engaging the larger diameter bore in a light interference fit which provides a'gas sealing action and minimizes the energy losses resulting from friction between the movable primer and the cartridge casing while at the same time providing a larger cross-sectional area throughout which the propellant gas can act. Alternatively, the light interference fit at the open flared obturator flange end may be a fit with a very small (e.g. up to approximately 0.005 inch) diametral clearnace relative to the base, as the flared obturator portion of the piston primer is readily deformable under the propellant gas pressure and this effects a seal and interference fit with the bore even in the instance of original small clearance. The forward longitudinal movement of the piston primer is limited by a stop formed in the larger diameter bore for engagement by the forward edge of the flared flange portion of the piston primer, while the rearward longitudinal movement of the piston primer is limited by the engagement of the back side of the flared obturating flange portion with the annular beveled shoulder connecting the coaxial bores.

When the head of a firing pin having a protrusion formed thereon strikes the base of the movable cupshaped piston primer at the end of a forward stroke, an indentation is formed in the relatively thin web-like base wall that ignites the primer charge which, in turn, fires the propellant to create a high gas pressure that propels a projectile from the cartridge casing while at the same time acting across the full cross-sectional area of the open end of the piston primer which occupies the full cross-sectional area of the larger diameter propellant-containing bore to exert a maximum force against the piston primer and drive it rearwardly. Since the obturating flange portion of the movable primer has only a small circumferential surface area engaging the larger diameter bore in an interference fit, and the deformation resistant cylindrical portion of the movable primer freely slidably engages the smaller diameter bore, the retarding frictional forces incurred during the rearward movement of the piston primer are minimized to enable it to drive the firing pin backward in a return stroke and transfer a maximum amount of energy to operate the breech mechanism, extract the spent cartridge, cock the firearm and chamber another cartridge.

Still other objects, features, and attendant advantages will become apparent to those skilled in the an FIG. 2 shows the cartridge of FIG. ll inserted in the chamber of a firearm with a bolt engaging the base of the cartridge and having a firing pin in the ready posi- HOD.

FIG. 3 is a view similar to FIG. 2, showing the firing pin striking the base of the movable primer and igniting the propellant to provide the projectile-propelling high gas pressure.

FIG. 4 is a view similar to FIGS. 2 and 3, showing the movable primer propelled rearward by the propellant gas pressure which forces the firing pin backward in a return stroke.

Referring now in detail to the figures of the drawings, in FIG. 1 is shown a cartridge suitable for use in a firearm which is operated on the primer set-back any energy transfer principle. The cartridge, generally indicated at 11, includes a casing, generally indicated at 13, containing a movable single-unit piston primer, generally indicated at 15, a projectile 21 and a propellant 31 disposed between the movable piston primer 15 and the projectile 21. The cartridge casing 13 has two coaxial bores of different diameters, indicated respectively at 13a and 13c, and connected through an annular beveled shoulder 13b, with the smaller guide bore being located at the rear or base of the cartridge casing 13 and the larger propellant-retaining bore 13a being located at the forward end of the casing I3 and adapted to securely grip an annular groove 21a of the projectile 21 by means of an annular indentation 13d.

The movable single-unit cup-shaped anvil-less piston primer 15 has an integral one-piece unitary cup having a cylindrical piston guiding portion 15a opening forwardly toward the interior of the larger diameter propellant containing bore 13a with an annular flared obturating flange portion 15b formed at the forward open end thereof, and with a web-like base wall formed integrally at and across the full rearward end thereof. The cylindrical piston guiding portion ll5a of the primer 15 is freely slidably disposed in the small diameter bore 130 at the rear of the cartridge casing 13 while the edge of the flared flange portion 15b slidably engages the larger diameter bore 13a in a light interference fit to provide a good movable gas pressure seal. In its unfired position, the edge of the flared flange portion 15b engages an annular forward shoulder stop as shown at 113e, or alternatively, circumferentially spaced dimple stops, which limit the forward motion of the primer piston.

Inside the thick-walled cylindrical, piston-guiding portion llSa is formed a cylindrical cavity 15d having a length generally greater than the diameter of the cylindrical cavity 15d, although this is not necessarily required. Compacted within the cylindrical cavity 15d is a primer charge 17 of a primer mixture, which may be of conventional primer mixture composition, which may if desired contain a small mixture of grit to enhance the reliability of firing of the primer at normal firing pin energy levels, although the grit is not necessary to operability, particularly at firing pin energy levels in the upper normal firing pin energy range. The de gree of compaction of the primer charge 17 is variable, but desirably it should be as great as possible without resulting in accidental ignition during the manufacture of the cartridge. The primer charge 17 contained in the cylindrical cavity 115d is separated from the propellant 31 contained in the larger diameter bore 13a of the cartridge casing by a thin, easily frangible, and preferably combustible moisture seal 19 of suitable material, such as a coating of wax or Krylon. While the moisture seal 19 is not absolutely required for functional operation, it is desirable to aid against malfunction due to undesired moisture absorption by the primer charge 17 which, for example, might occur during assembly.

The integral one-piece cup-shaped body of primer may be suitably formed of various materials, dependent upon the tensile strength required, it being of course necessary that the primer retain its body integrity when fired, so as to maintain a propellant gas seal with a cartridge in which it may be fitted or formed. For peak propellant burning pressures of the order of approximately 50,000 70,000 psi a high tensile strength steel such as medium to high carbon steel (e.g. 1050 steel, 1065 steel), heat treatable alloy steels and precipitation hardening steels are suitable. For lower peak propellant pressures as of the order of 40,000 psi or less, the cup body of primer 15 may be formed of brass or other material of lower tensile strength properties.

In FIGS. 2-4 is illustrated the operation of the cartridge 11 shown in FIG. 1. In FIG. 2 the cartridge 11 is shown inserted in a chamber 41a of a conventional barrel 41 with a bolt 51 pressed against the base of the cartridge casing 13 and having extractor fingers 51a engaging an extractor groove 13f formed in the rear of the cartridge casing 13. Disposed inside the bolt 51 is a firing pin 61 having a head 61a with a protrusion 61b in the center thereof for striking the easily deformable and relatively thin web-like base wall 15c of the cupshaped piston primer 15 to ignite the primer charge 17 and fire the propellant 31.

In FIG. 3 is shown the head 61a of the firing pin striking the relatively thin-walled web-like base wall 150 of the movable piston primer 15 at the end of a forward stroke. The protrusion 61!) formed on the head 61a of the firing pin 61 makes an indentation in the integral and closed web-like base wall 150 of the piston primer 15 to ignite the primer charge 17. The utilization of all of the available energy of the forward stroke of the firing pin 61 to form an indentation in the integral weblike base wall 15c of the piston primer 15 is insured by the engagement of the end of the annular flared flange portion 15b of the piston primer 15 with the annular shoulder 13:: formed in the large diameter bore 13a which prevents forward movement of the piston primer 15.

The exact manner in which the primer charge 17 is ignited without the requirement for an anvil is not fully understood, but it is thought that the indentation formed in the relatively thin-walled web-like integral and continuous base wall 150 of the movable anvil-less integral unitary piston primer 15 causes primer ignition through imparting relative movement between particles in the primer charge 17, as by causing a column of primer charge particles in the cylindrical cavity 15d to move in relation to other primer charge particles nearer the periphery of the cylindrical cavity 15d which remain generally stationary due to the friction between the primer charge 17 and the wall of the cylindrical cavity 15d, and that the resulting abrupt friction between the moving and stationary primer charge particles generates a sufficient heat to ignite the primer charge 17, or as by abrupt relative motion and compaction of a quantity of primer particles at the rear end of the primer charge cavity adjacent integral closure web 15c with these rear centrally disposed particles being moved in compaction against the restraint exerted by the remaining forward mass of primer charge particles in the highly compacted columnar mass 17 of primer charge particles.

However, irrespective of the theory by which the primer charge 17 is ignited, the anvil-less ignition of the primer charge 17 ruptures the moisture seal 19 and fires the propellant 31 which generates a high gas pressure that propels the projectile 21 forward with sufficient force to disengage the annular indentation 13e which grips the annular groove 21a of the projectile 21. In addition, the high pressure propellant gas obturates the annular flared flange 15b of the primer 15 against the large diameter bore 13a of the cartridge casing 13, thereby preventing gas leakage to the rear of the movable piston primer 15, and at the same time act across the full cross-section area of the propellant chamber to impart a maximum amount of rearward force to the primer. Since the cylindrical piston portion 15c has a relatively thick-walled deformation resistant construction, it resists expansion by the high gas pressure against the propellant 31, and remains easily slidable within the small diameter bore to deliver a maximum amount of force to the firing pin 61 to drive it backward in a return stroke.

Since a sufficient identation must be made in the web-like base wall 15c of the piston primer 15 to ignite the primer charge 17, yet not exceed the elongation or shear limits of the material, the contour of the protrusion 61b formed on the head 61a of the firing pin 61 are of importance. The diameter and the amount of the protrusion formed on the surface of the head must be sufficient to cause adequate compacting or internal relative movement of the primer charge particles within the cavity 15d to cause ignition of the primer charge, yet the annular edges or corners such as at 61c, 61d on the protrusion 61b should be rounded or chambered to prevent shearing failures of the relatively thin web-like base. Also the diameter of the head 61a of the firing pin 61b preferably extends across the rear face of the primer 15 to provide an adequate support for the piston primer to prevent upon ignition, possible rupture by the resultant high pressure propellant gas.

As the cup-shaped anvil-less piston primer is propelled rearwardly by the high pressure propellant gas, it drives the firing pin backward in a return stroke to operate the breech mechanism and/or other components of the firearm. Initally the relatively thin-walled web-like base 15c is prevented from rupturing due to the support provided by engagement with the base of the firing pin.

Upon engagement of the flared flange portion 15b with the beveled shoulder 13b, the rearward motion of the piston primer stops and the head of the firing pin 61 no longer provides support for the relatively thin web-like base wall since it continues its rearward motion, however, the forward motion of the projectile 21 through the barrel 41 increases the volume throughout which the propellant gas can expand and consequently when the rearward motion of the piston primer stops the propellant gas pressure is reduced sufficiently to eliminate a possible rupture of the relatively thin web-like integral base wall 150 the present of the piston primer.

In one preferred mode of practicing the present invention, and integral piston primer is formed from 1065 steel which is heat treated to R 32-36 and having a cylindrical wall 15a of an outer diameter of 0.l70 inch, an obturating flared flange portion 15b of a diameter of 0.223 inch, and a relatively thin web-like base wall 150 of 0.014 inch thick. A cylindrical cavity 15d is formed inside the piston primer with a diameter of 0.093 inch. Inside the cavity, 0.04 gram of dried primer charge are compacted with a pressure of the order of from 125,000 to 175,000 psi, and the length/diameter ratio of the cylindrical primer charge 17 is in the range of approximately 1.5 to 2. The preferred embodiment primer mixture composition consists of the following ingredients in the indicated proportions;

EXAMPLE I Ingredient Dry Wt.

Lead Styphnate, Normal (sensitive high explosive) 37 i Tetracene (sensitive high explosive) 4 i l Barium Nitrate (oxidizer) 32 i 5 Antimony Sulfide (abrasive & exothermic fuel) l5 1 2 Aluminum Powder (exothermic fuel) 7 i l PETN (Class 2) (high energy yield explosive) 5 i 1 This is a composition now generally known as FA- 956, except that it does not include a light gum solution which is normally utilized in FA-956 per se.

An alternative workable composition is as follows:

EXAMPLE II Ingredient Dry Wt. Lead Styphnate, Normal (sensitive high explosive 31 percent Barium Nitrate (oxidizer) 19 percent Antimony Sulfide (abrasive & exothermic fuel) 20 percent Lead Dioxide (oxidizer) 8 percent Tetracene (sensitive high explosive) 10 percent Zirconium (catalyst) 8 percent PETN (Class 2)(high energy yield high explosive) 4 percent With the illustrative example, the associated firing pin used in conjunction with the cartridge impacts the movable primer with an input energy of 48 inch-ounces and has a diameter of 0.155 inch with a protrusion extending approximately 0.012 inch from the head of the firing pin with a diameter of 0.060 inch. The base radius of curvature 61d of the protrusion 61b on the firing pin 61 is 0.020 inch, while the radius of curvature at the extended rim surface 61c of the protrusion is 0.005 inch.

While the invention has been illustrated and described with respect to a single preferred embodiment, it will be apparent to those skilled in the art that other embodiments and various modifications and improvements may be made without departing from the scope and spirit of the invention. For example, the cavity within the relatively thin-walled cylindrical piston por-' tion of the primer may not necessarily be cylindrical but may assume a variety of shapes. Also, the moisture seal need not be combustible but may be of very thin relatively non-combustible easily frangible material such as Chapman's red lacquer, epoxy or metal foil which offers substantially no resistance analogous to or which in any manner would function as an anvil for the ignition of the primer mix. In addition, while the illustrative cartridge provides full utilization of all aspects of my invention, including a cartridge with a movable one-piece anvil-less piston primer, it will be appreciated that a fixed primer/cartridge construction may be embodied, with or without the obturating flange. Accordingly, it is to be understood that the invention is not to be limited by the single preferred, illustrative embodiment, but only by the scope of the appended claims.

That which is claimed is:

1. In a cartridge of the primer set-back type including a casing having an open forward end with a projectile fastened therein, containing a propellant and having a bore formed in the base portion with a movable piston primer disposed therein and adapted for longitudinal movement along the axis thereof, the improvement comprising:

said primer being devoid of an anvil and having an integral one-piece cup-shaped piston formed of malleable material of a character and a thickness to maintain its body integrity when fired yet sufficiently thin-walled at its closed base to enable percussive dimpling thereof by a firing pin, said integral one-piece cup-shaped piston containing a primer mixture and being open at the forward end toward the propellant and cartridge casing.

2. In a cartridge of the primer set-back type according to claim I, wherein sad piston primer further comprises:

a tubular wall portion engaging the bore in the base of the cartridge in a free sliding fit, and

a web-like base wall formed integrally at and closing the rearward end of said tubular wall portion and being relatively thinner and more easily deformable than said tubular wall portion and adapted to have an indentation formed therein upon being struck by the head of a firing pin to effect percussion ignition of the primer mixture contained therein.

3. In a cartridge of the primer set-back type according to claim 2, the improvement further comprising a forward stop-retaining means being formed in the cartridge casing and adapted to engage the open end of said piston primer to limit the forward movement thereof and thereby enabling a major quantity of the energy associated with the forward stroke of a firing pin to be utilized to form an indentation in the web-like base of the cup-shaped primer to effect percussion ignition of the primer mixture.

4. In a cartridge of the primer set-back type according to claim 3, the improvement further comprising:

said cartridge casing having a second bore formed therein of larger diameter and coaxial with the first bore and adapted to contain said propellant therein, and

an annular flared obturating flange portion formed at the open end of said cup-shaped piston primer and disposed in the large diameter bore of the cartridge casing with the sides of the flanged portion engagable with the larger diameter bore in interference sealing relation during rearward travel thereof as a function of the pressure of the propellant gases upon ignition of said propellant.

5. In a cartridge of the primer set-back type according to claim 4:

the edge of said annular flared flange portion having a thickness substantially less than the thickness of the tubular flange portion. I

6. In a cartridge of the primer set-back type according to claim 4, the improvement further comprising:

an annular beveled shoulder connecting said first and second coaxial bores formed in the cartridge casing, and

the back side of the annular flared flange portion formed at the open end of the cup-shaped piston primer being adapted to engage said annular beveled shoulder connecting the coaxial bores formed in the casing to limit the rearward movement of the cup-shaped piston primer upon ignition of the propellant charge.

7. A cartridge having a percussive primer disposed therein, and flash ignitable propellant charge disposed within said cartridge and adjacent and forward of said 10 percussive primer, said percussive primer comprising:

said primer mixture comprising the mixture of Example I.

an integral unitary cup-shaped body formed of malleable material having a composition and thickness to maintain its body integrity when the primer is 10. A cartridge according to claim 7,

said primer mixture comprising the mixture of Example ll.

11. A cartridge according to claim 7,

fired, yet sufficiently thin-walled at its rear end to 7 enable percussive dimpling thereof by a firing pin, Sald compact Emmet an exploswe said integral unitary cup shaped body having a powder constltuent, or oxidizer constltuent, and an compact primer mixture retained therein by comabras've pact frictional gripping with the side walls of said A qartrldgq according to claw cup-shaped body portion being effectively open at Sald Pnmer mlxmre further compflsmg F h/ i f rd d d d id f an il constituent for increasing exploslve reaction rate id h d b d h i a l d d f bl between said explosive powder and said oxidizer.

rear end, and 13. A cartridge according to claim 7, said compact primer mixture being ignitible b said integral unitary cup-shaped body being formed abrupt percussive external inwardly directed deforas an integral unit of malleable metal. mation of said closed rear end.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5,7 H Dated July 1 1975 Inventor(s) Irwin R. Barr It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line LI, "now abandoned" should be deleted and filed Aug. 15, 1969 substituted therefor;

line 5, "Aug. 15, 1969" should be deleted and now abandoned substituted therefor.

Column 2, Line 29, "thereby enabling" should not appear between "to" and "be".

Column 3, L in 2 0, "clearnace" should be --clearance--- Column 4, I ine l 5 "any" should be "and".

Column 6, Line 39, should have a comma after "also".

Qglu mr 1 "the present" should not appear between "15c" and "of".

Claim 3, Line 2, requires colon after "comprising".

Signed and sealed this 13th day of May 1975.

4 (SEAL) l Attest:

- C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks ORM PO-1050 (10-69) USCOMM-DC eoa1ee9 11.5 GOVERNMENT PRINTING OFFICE 1 9 93 o UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO. D d 10,

Inventor(s) Irwin R. Barr It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line A, "now abandoned" should be deleted and filed Aug. 13, 1969 substituted therefor;

line 5, "Aug. 13, 1969" should be deleted and now abandoned substituted therefor.

Column 2, Line 29, "thereby enabling" should not appear between "to" and "be".

Column 3, L in e 2 "clearnace" should be ---clearance--- Column 4, Lineii, "any" should be "and".

2 olumn 6, Line 39, should have a comma after "also".

C2 lu mn 6 Ling-12ft, "the present" should not appear between "15c" and "of".

Claim 3, Line 2 requires colon after "com risin P 8 Signed and sealed this 13th day of May 1975.

I (SEAL) l Attest C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks USCOMM-DC 60376-F69 us eovzumazm PRINTING omcs: 93 o ORM PO-1050 (10-69) 

1. In a cartridge of the primer set-back type including a casing having an open forward end with a projectile fastened therein, containing a propellant and having a bore formed in the base portion with a movable piston primer disposed therein and adapted for longitudinal movement along the axis thereof, the improvement comprising: said primer being devoid of an anvil and having an integral onepiece cup-shaped piston formed of malleable material of a character and a thickness to maintain its body integrity when fired yet sufficiently thin-walled at its closed base to enable percussive dimpling thereof by a firing pin, said integral onepiece cup-shaped piston containing a primer mixture and being open at the forward end toward the propellant and cartridge casing.
 2. In a cartridge of the primer set-back type according to claim 1, wherein said piston primer further comprises: a tubular wall portion engaging the bore in the base of the cartridge in a free sliding fit, and a web-like base wall formed integrally at and closing the rearward end of said tubular wall portion and being relatively thinner and more easily deformable than said tubular wall portion and adapted to have an indentation formed therein upon being struck by the head of a firing pin to effect percussion ignition of the primer mixtUre contained therein.
 3. In a cartridge of the primer set-back type according to claim 2, the improvement further comprising: a forward stop-retaining means being formed in the cartridge casing and adapted to engage the open end of said piston primer to limit the forward movement thereof and thereby enabling a major quantity of the energy associated with the forward stroke of a firing pin to be utilized to form an indentation in the web-like base of the cup-shaped primer to effect percussion ignition of the primer mixture.
 4. In a cartridge of the primer set-back type according to claim 3, the improvement further comprising: said cartridge casing having a second bore formed therein of larger diameter and coaxial with the first bore and adapted to contain said propellant therein, and an annular flared obturating flange portion formed at the open end of said cup-shaped piston primer and disposed in the large diameter bore of the cartridge casing with the sides of the flanged portion engagable with the larger diameter bore in interference sealing relation during rearward travel thereof as a function of the pressure of the propellant gases upon ignition of said propellant.
 5. In a cartridge of the primer set-back type according to claim 4: the edge of said annular flared flange portion having a thickness substantially less than the thickness of the tubular flange portion.
 6. In a cartridge of the primer set-back type according to claim 4, the improvement further comprising: an annular beveled shoulder connecting said first and second coaxial bores formed in the cartridge casing, and the back side of the annular flared flange portion formed at the open end of the cup-shaped piston primer being adapted to engage said annular beveled shoulder connecting the coaxial bores formed in the casing to limit the rearward movement of the cup-shaped piston primer upon ignition of the propellant charge.
 7. A cartridge having a percussive primer disposed therein, and flash ignitable propellant charge disposed within said cartridge and adjacent and forward of said percussive primer, said percussive primer comprising: an integral unitary cup-shaped body formed of malleable material having a composition and thickness to maintain its body integrity when the primer is fired, yet sufficiently thin-walled at its rear end to enable percussive dimpling thereof by a firing pin, said integral unitary cup-shaped body having a compact primer mixture retained therein by compact frictional gripping with the side walls of said cup-shaped body portion being effectively open at its forward end and devoid of an anvil, said cup-shaped body having a closed deformable rear end, and said compact primer mixture being ignitible by abrupt percussive external inwardly directed deformation of said closed rear end.
 8. A cartridge according to claim 7, said primer mixture having a frangible covering thereon between said primer mixture and said propellant charge, and said primer being devoid of an anvil structure between said primer mixture and said propellant charge.
 9. A cartridge according to claim 7, said primer mixture comprising the mixture of Example I.
 10. A cartridge according to claim 7, said primer mixture comprising the mixture of Example II.
 11. A cartridge according to claim 7, said compact primer mixture comprising an explosive powder constituent, or oxidizer constituent, and an abrasive constituent.
 12. A cartridge according to claim 11, said primer mixture further comprising a catalyst constituent for increasing explosive reaction rate between said explosive powder and said oxidizer.
 13. A cartridge according to claim 7, said integral unitary cup-shaped body being formed as an integral unit of malleable metal. 